1. Field of the Invention
The present invention relates to an imaging device and an imaging method, and particularly relates to a shading correction technology.
2. Description of the Related Art
In some cases, luminance unevenness (shading) may occur between a central portion and a peripheral portion of an image, which is captured by an imaging device such as a digital camera, due to characteristics of an optical system (such as a lens). Accordingly, there have been proposed various methods for correcting shading.
For example, JP2006-115191A discloses an imaging device including: accumulation start control means for controlling start of photoelectric charge accumulation of an imaging element; and accumulation end control means for controlling end of the accumulation of the imaging element by transmitting the photoelectric charge of the light receiving portion to a temporary accumulation section. In this imaging device, control timing of the accumulation start control means and/or the accumulation end control means is changed for each pixel or for each line, and a time period of accumulating photoelectric charge for each pixel or for each line is controlled, thereby correcting shading of a captured image.
JP-S64-039178A discloses an imaging device including an image sensor that is configured to perform photoelectric conversion on an optical image and perform nondestructive reading. In this imaging device, light signals of a single frame are read from the image sensor multiple times, and are sequentially added up, and an integrated output signal is output when the number of adding operations reaches a predetermined number. Thereby, a limitation of a Signal-Noise ratio (SN ratio) of an amount of light incident into the image sensor is improved, and thus high sensitivity is achieved.
In addition to the shading correction, there are proposed various imaging processing methods for improving image quality of a captured image.
For example, JP2008-271368A discloses an imaging device including: an imaging section that outputs a captured image signal formed of a long-exposure image signal and a short-exposure image signal; and a signal processing section that generates a synthesized image signal in which the long-exposure image signal and the short-exposure image signal are synthesized and which has a wide dynamic range. In this imaging device, exposure control is performed in accordance with a user setting exposure mode, and automatic exposure control for the short-exposure image signal is performed using luminance information of the synthesized image signal. Thereby, a problem of white color in the setting exposure mode is solved.
JP2011-243704A discloses a solid-state imaging device in which a gate electrode of the signal reading circuit includes a signal conversion transistor and the signal conversion transistor is connected to a photoelectric conversion section. This photoelectric-conversion-film-laminated-type solid-state imaging device prevents noise from being mixed with the signals at the time of electric charge accumulation.